Abstract: The invention relates to a rotary encoder (10) for a machine, in particular a hoist, crane or the like, and to a method for operating a rotary encoder, the rotary encoder having a rotary encoder shaft (12) which is connectable to a shaft of a machine for detecting a rotation of the shaft, the rotary encoder having a frame (11) which is mountable on a machine, the frame (11) having an encoder element (13) disposed thereon for detecting a rotation of the rotary encoder shaft and a signal output element (14) for outputting a rotation angle signal and/or a speed signal, the rotary encoder having a bearing device (20) by means of which the rotary encoder shaft is rotatably mounted on the frame, the rotary encoder having an insulating device (19) which electrically insulates the rotary encoder shaft and the bearing device from the frame.